1. Field of the Invention
The present invention relates to a solar cell, and more specifically, to the structure of a lead-out electrode. This application claims the benefit of priority from Japanese Patent Application No. 2011-216948, filed Sep. 30, 2011, the content of which is incorporated herein by reference in its entirety.
2. Description of the Related Art
Solar cells are roughly classified into silicon-based cells, compound-based cells, and organic cells according to a material for a light absorbing layer (power generation layer). Among these solar cells, dye-sensitized solar cells (hereinafter referred to as “DSCs”) include a power generation electrode (negative electrode) in which a semiconductor layer (for example, TiO2) carrying a sensitizing dye is formed, an opposite electrode (positive electrode) with catalyst metal formed therein, and an electrolyte sandwiched between the power generation electrode and the opposite electrode and containing iodine redox (see, for example, FIG. 13 of Japanese Patent Laid-Open No. 2010-211971 shown below). A power generation mechanism of the DSC acts according to the following cycle (1) to (4).    (1) When solar light enters a light receiving surface, electrons are excited in the dye due to absorption of energy.    (2) The excited electrons migrate to the TiO2, which forms the semiconductor layer, further pass through a transparent electrode to the outside (on the negative electrode side).    (3) The dye having lost the electrons draws electrons from the electrolyte.    (4) The electrolyte having lost the electrons to the dye takes electrons from the positive electrode.
Advantageously, the above-described dye-sensitized solar cell depends on the angle of incident light less significantly than the conventional solar cells (silicon-based cells, compound-based cells, and the like) and can generate power even with weak light such as indoor light. In connection not only with the dye-sensitized solar cell but also with all the other solar cells, a practical solar cell panel is supplied with power by a plurality of solar cells connected together in series-parallel. In this case, even if only some of the solar cells are degraded, the characteristics of the whole panel are significantly deteriorated. Thus, the ability to exclusively replace the degraded solar cells is advantageous for maintaining the characteristics of the whole panel.
Japanese Patent Laid-Open No. 2010-211971 shown below discloses a dye-sensitized solar cell including a first substrate with a first thin-film electrode, a second substrate with a second thin-film electrode, a semiconductor layer which contacts one of the first thin-film electrode and the second thin-film electrode and on which a dye is adsorbed, an insulating spacer disposed between the first thin-film electrode and the second thin-film electrode arranged opposite each other, and an electrolyte filled in a space enclosed by the first thin-film electrode, the second thin-film electrode, and the insulating spacer, wherein a substrate for a positive electrode is processed so as to form processed holes (through-holes) therein so that lead-out electrodes are oriented in the same direction so as to be easily led out. Furthermore, Japanese Patent Laid-Open No. 2005-222995 shown below discloses that two electrodes of a dye-sensitized solar cell are led out in the form of plugs and that a connection substrate side for modularization is shaped like a socket, thus improving the connectivity of the unitary cell. This enables a user to select the number and sequence of mounted units according to the user's need.